Isolated lateral meniscus tear masquerading as a potential septic arthritis in a 7 year old

A 7-year-old boy presented with a 1-week history of a limp, low grade temperature and mildly elevated inflammatory markers. He sustained a fall 2 weeks ago but was relatively symptom free for a week. The inital physical exam demonstrated a knee effusion clinically, radiographs did not demonstrate any overt pathology and biochemical testing demonstrated an elevated C reactive protein of 8 mg/L. An arthroscopy was conducted, with a plan for synovial biopsies to investigate for infective versus inflammatory arthritis as a cause for the effusion. An isolated lateral meniscal tear was discovered. This was repaired using all inside technique with Smith and Nephew's FastFix 360 (R) suture anchors. It is quite uncommon to find isolated lateral meniscus tears in this population, but the learning point demonstrates it is important to arthroscopically examine the whole knee, even while performing synovial biopsies as there may be unexpected findings.